Optical fiber connectors are an essential part of practically all optical fiber communication systems. For instance, such connectors are used to join segments of fiber into longer lengths, to connect fiber to active devices such as radiation sources, detectors and repeaters, and to connect fiber to passive devices such as switches and attenuators. The principal function of an optical fiber connector is to optically couple a fiber with a mating device (e.g., another fiber, an active device or a passive device). This is achieved by holding the end of the fiber such that the core of the fiber is axially aligned with the optical pathway of the mating device.
To facilitate an effective optical coupling, the end face of the ferrule is typically polished. Furthermore, a family of special connectors have ferrules that are polished at an angle to reduce return loss, which is the ratio of input power to reflected power. These connectors are referred to as angled physical contact (APC) connectors. By polishing the ferrule at an angle, light that is reflected at the face of the ferrule is reflected at an angle into the cladding of the fiber, rather than back down the fiber core where it can interfere and diminish forward-propagating optical signals. An APC angle is usually about 7 to 12 degrees.
Preparing a polished ferrule is a sophisticated process. It requires cleaving the fibers, terminating them in a ferrule, and polishing the ferrule to exacting tolerances. Therefore, such a process is usually performed in a controlled setting with precision equipment by skilled personnel. Frequently, however, connectors must be terminated in the field where such facilities and personnel are not available. Under these conditions, it is desirable to omit the step of the polishing the ferrule by instead terminating the fiber in a connector which has a fiber stub already terminated in a polished ferrule. Because the ferrule is already polished in a fiber-stub, field-installable connector, field installation requires only optically coupling the fiber to the fiber stub. This is often done with using a refractive index matched gel to improve optical coupling therebetween.
Although field-installable connectors eliminate the need to polishing the ferrule in the field, terminating the fiber to the connector can nevertheless be difficult in the field, where conditions often require the installer to perform this operation without a workbench and using handheld tools. Indeed, the operation is often performed while standing.
Furthermore, the task is even more difficult for an APC connector in which the fiber stub is angle cleaved, requiring the terminating fiber to be angle-cleaved too. The angle-cleaved terminating fiber should be rotationally aligned with the stub to optically couple properly. If there is even slight rotational misalignment (e.g., 15 degrees), the angled end faces of the stub and terminating fiber will interfere and create a longitudinal gap between the two fibers. These gaps tend to significantly increase insertion losses in certain situations. Therefore, to properly terminate an APC fiber in the field, it must be cleaved at the same angle as the stub and rotationally aligned with the stub. However, keeping the fiber oriented with the connector is complicated by the fact that the angle of the cleave cannot be perceived by the naked eye. Consequently, rotational misalignment of the fiber is often discovered only after the fiber is terminated due to poor optical performance. Discovering problems at this stage requires that the fiber be re-terminated, which wastes not only time, but also the connector if the field-installable connector design can only be terminated to a fiber once.
Therefore, an approach is needed for simplifying field terminations, especially APC-type connector terminations, which ensures that the fiber is cleaved precisely and rotationally aligned with the connector. The present invention fulfills this need among others.